This K08 application plans to study the regulation of fimbriae in the gram negative oral pathogen, P. gingival is. This putative period onto pathogen has been studied extensively and a large number of virulence factors have been determined. However, few if any of them have been observed to function in vivo. The fimbriae of P. gingival is are considered to be a structural virulence factor since loss of these structures results in poor to no adherence the bacterium to host cells. Since the ability of a bacterium to adhere to host cells is an essential first step in host-associated bacterial virulence, loss of this function is critical to survival or the health and well being of the host. The structural gene for fimbrillin, the subunit protein which forms the fimbriae structure, has been cloned and sequenced from nine P. gingival is strains. In addition to the genetic studies, the fimbriae from this bacterium have been extensively studied immunologically, chemically and structurally.